How Long are Betta Fish Pregnant?

While betta fish do not give birth to live young such as mollies or lyretails, they do become pregnant with eggs. The female approaches the male during the egg release and the male betta then fertilizes the eggs outside of the female’s body. The female betta will carry the eggs in her body between 1 – 2 weeks before she releases them – a process known as spawning. 

Read on to learn how to figure out if your betta fish is pregnant, how betta fish reproduce, whether you can have a breeding pair, and more.

How do I Know if my Betta Fish is Pregnant?

While pregnancy isn’t a completely accurate term for a betta fish who is carrying unfertilized eggs, it is still used to avoid confusion among aquarium enthusiasts. Experts refer to the state of a female betta fish carrying eggs as the gravid state.

Female betta fish have an organ called an ovipositor, upon which forms a white dot and white stripes on her sides when she is fixing to lay eggs. Her belly also becomes swollen when eggs are developing inside her body.

If your female betta has a swollen belly but no white marks are present, then she may be constipated or overweight. If this is the case, make sure to evaluate your betta’s diet.

Since the eggs are not fertilized when the female betta releases them from her body, a single female betta in a tank might lay several clutches of eggs throughout her reproductive cycle.

What do I do if my Betta Fish is Pregnant?

If you notice that your betta fish is indeed pregnant, you don’t have to do anything unless there is a male betta nearby. The female betta carries unfertilized eggs for the male to fertilize outside of her body. It is very common for a female betta alone in a tank to lay eggs several times throughout her reproductive cycle, even when there is no male present.

If you plan on breeding your betta fish and your female is developing eggs, then bring your male betta into the tank – never keep male and female betta fish together in the same tank except during breeding times.

Bubble Nests

If the male is ready to mate, he will form what is called a “bubble nest” – a small, foamy nest made of bubbles floating on the surface of the water that he uses to entice the female to lay her eggs.

Once the male builds the nest and the female approves of it, they will mate by “embracing” and sinking toward the bottom of the tank. Once the eggs are fertilized, they will float into the bubble nests, where the eggs will be protected in an oxygen-rich environment until they hatch.

Because bubbles periodically pop, the male betta will maintain the nest by adding new bubbles to the nest each time he goes up for air. If there are other males present (which is almost exclusively in the wild, as most betta enthusiasts know not to put more than one betta in a tank), he will defend his bubble nest and the surrounding area against rival males.

The presence of a female in the tank will drive the male to build a nest faster in anticipation of their mating.

Sometimes a female will not approve of the bubble nest her mate has built and will destroy it, prompting the male to build a new nest.

How Fast do Betta Fish Reproduce?

Each breeding period usually lasts about 2 weeks. The beginning of this period includes the female developing eggs (which can take 1 – 2 weeks to spawn) and the male creating the bubble nest.

After spawning, there is an aggressive period of 2 – 3 days before the bettas mate. After mating, the female is no longer involved in the process. The male watches over the nest, replacing popped bubbles and fallen eggs, until they hatch. The eggs can take between 36 – 72 hours to hatch as fry.

The male will continue to watch over the fry until they can successfully swim, which takes another 36 hours after hatching.

Can I Have a Breeding Pair of Betta Fish?

Since betta fish can be very aggressive, even toward their prospective mates, experts recommend keeping male and female bettas separate until they are ready to mate. You will know when your fish are ready to mate when the female grows a swollen belly, a result of the eggs developing in her ovipositor.

When adding a female to the male’s tank or vice versa, watch the pair carefully. Sometimes the male, in his eagerness to impress the female and mate with her, will crowd her and stress her out. If she isn’t yet prepared to spawn, the male may grow aggressive with her, which will cause the female more stress and make it more difficult to her to spawn.

The best course of action with breeding your fish is to keep the male and female in separate tanks until the female begins to show signs of spawning. This way, when you introduce her into the male’s tank, she will be ready to spawn and there will be decreased chance of the male causing her stress.

Do Betta Fish Eat their Young?

Unlike most fish, which will spawn their eggs and leave them on their own, bettas provide extra care and attention to their offspring. They do not eat their eggs or their fry except for in times of starvation or extreme duress.

Not only do bettas build nests to protect their eggs from predators and the elements, but they will defend their offspring against predators. While the female is uninvolved in the process once she has spawned, the male will maintain the nest and guard the fertilized eggs until they hatch.

It is common for both males and females to eat unfertilized eggs. Sometimes you will see the male eating eggs from the nest, but these eggs are usually unfertilized and have started to rot.